Osteoarthritis (OA), the leading cause of disability in the United States, has a significant impact on quality of life. Knee OA alone affects approximately 6% of the US adult population. In patients with severe knee OA total joint replacement JJR) surgery is considered an extremely valuable intervention, which relieves chronic pain, restores lost function, and is cost effective. Recent reports, however, indicated that TJR may be underutilized and that utilization varies widely by race/ethnicity and gender. For instance, women have significantly worse preoperative functional status at time of TJR for OA, suggesting they choose TJR at a more advanced disease stage, possibly at the expense of quality of life. To date, findings to explain these disparities are inconclusive, but our preliminary data supports the view that differences in the amount of perceived social support may contribute to the different utilization patterns. Based on results of our pilot studies, we hypothesize that social support may be critical in understanding race/ethnicity and gender differences in TJR rates. Specifically, 1) prior to surgery, perceived and actual social support affect TJR acceptance rates differently and this difference varies by race/ethnicity and gender, and 2) more perceived social support is related to less self-reported disease severity, which ultimately affects the TJR acceptance rates. We will conduct a prospective longitudinal study of 320 subjects with severe knee OA who are TJR candidates to establish measures of social support, disease activity, and functional status. This team will use results from the proposed study to generate a future longitudinal study to aid in developing an intervention to promote earlier clinical treatment for those individuals who are prone to wait until more advanced stages of disease before considering TJR. The results of such a study could be applied to the understanding and treatment of other chronic conditions.